Electrical apparatus



April 27, 1954 KNuDsoN ELECTRICAL APPARATUS Filed Sept. 30, 1947INVENTOR.

(2411, a. Baum/z,

ATTORNEY Patented Apr. 27, 19,54

ELECTRICAL APPARATUS Lewis I. Knudson, Sidney, N. Y., assignor to BendixAviation Corporation, New York, N. Y., a corporation of DelawareApplication September 30, 1947, Serial No. 776,904

3y Claims. (Cl. 317-206) This invention relates to .electrical apparatusand more particularly to an induction device adapted for use by Way ofexample in apparatus for investigating the operation of the ignitionsystern of an internal combustion engine or the like.

One of the objects of the present invention is to provide a novelapparatus for magnetically, i. e., inductively picking up electricalenergy from an electrical conductor which means are so constructed as tosubstantially eliminate the effects of capacity components.

f Another object of the invention is to provide novel apparatus of asimpliiied nature which may be readily associated with an electricalconductor and adapted to respond to changes in the flow of energythrough the conductor.

A further'object is to provide a novelly constructed radio shielded unitfor picking up energy by induction -from a single electrical conductorand which may be readily associated with a radio shielded conductor.

Still another object is to provide a novel transformer device which maybe readily and quickly inserted in the input lead for an internalelectric spark plug or other electrical conductor for generating signalsin a circuit which is wholly free of direct electrical connection tosaid conductor, said signals being in response to voltage variations insaid conductor.

The above and further objects and novel features of the invention willmore fully appear from the following detailed description when the sameis read in conjunction with the accompanying drawing. It is to beexpressly understood, ho-wever, that the drawings are for the purpose ofillustration only and are not intended as a dennition of the limits ofthe invention, reference for this latter purpose being had primarily tothe appended claims.

In the drawings wherein like reference characters refer to like partsthroughout the several views,

Fig. 1 is a side elevational view partly in section and with partsbroken away showing one form of device embodying the invention.

Fig. 2 is a detail elevational view with parts broken away and partly insection showing the coil and core structure of the device shown in Fig.1` as viewed from the right in said figure; and

f l'igy3 is a section taken substantially on lin 3 3 of Fig. 2.

Thesingle embodiment of the invention illustrated in the drawings, byway of example, is designed for use in conjunction with a radio shieldedignition system of an internal combustion engine but it'A is to be'understood that the invention is not limited to use in suchenvironnient.; The-device as shown comprises Va metallic casing 5 whichserves as a shield for intercepting electrical and magnetic emanationswhich would interfere with radio reception and may be fabricated in anysuitable manner, and said casing is preferably provided with oppositelydisposed outlets or openings 6 and l for the the passage of an electricconductor 8 which is preferably insulated as shown. In order thatconductor 8 may be conveniently and quickly inserted in a spark plugcircuit, for example, of an ignition system, outlet E is adapted forconnec tion with a. short length of flexible metallic tubing 9 throughwhich cable 8 may extend and terminate in a plug connector (not shown)of the type commonly used for making connection to a shielded sparkplug.v Outlet 'l is adapted to threadedly receive a barrel or socket(not shown) of the type found on shielded spark plugs in common use andadapted to receive the terminal of l a spark plug lead for connectionwith the other end of cable 8.

A novelly constructed induction coil unit is mounted within casing 5 inoperative relation to cable 8 in such a manner that the coil thereofwill be energized in response to variations in the flow of current inthe cable and so that the current picked up by the coil willbe-substantially free of capacity components. The illustrated coil unitcomprises a two-part laminated core ill-l0, the two U-shaped parts ofwhich are secured together in any suitable manner such as by: means of ametallic strap I l and a clamp l2 which joins the ends of the strap toform a continuous ring shaped metal core of metallic i'lux conductingmaterial. The conductor 8 passesthrough the central opening in core I0so that the latter will serve as a path for the lines of magnetic iluxcreated around the conductor by the flow of current there-y through Corei0, I0 ma-y be fabricated by first wrapping a continuous metal striparound a mandrel having the desired size and thereafter cutting the sameinto two parts to permit mounting of the coil to be next described. Itwill be understood. of course, that the core may be fabricated in otherknown ways and, if desired, thev laminations Imay-.extend at rightangles to those illustrated and consister" flat rectangu* lar stampings,split for mountingin a pre-wound coil. f i -1 A coil i4 has a windingl5-which surrounds a section of one of the U-shaped parts of core l0,the same being tightly wound on an insulating sleeve i6 and between twoinsulating end guides I'l-Il. Said sleeve and guides may be cemented tothe core structure or otherwise suitably secured in place thereon. In asuitable embodiment for use in the spark plug circuit of a largeaircraft engine, coil winding I5 was constituted by about 1400 turns ofNo. 38 or No. 40 copper 3 wire. As shown, the ends of winding I5 areconnected by means of leads I8 and I9 to a pair of terminals of a plugandsocket connector, only the plug part of which is illustrated as beingsecured in an opening in the wall of casing 5. 1f desired, the lowpotential end of the coil winding may be connected to ground throughcasing 5. Core i0 is also yconnected to ground by a lead 2! which issoldered or otherwise suitably secured to the casing at 22.

1n order to substantially eliminate the capacity components in thecurrents induced in coil I4, a discontinuous metallic sleeve 23,vpreferably a steel sleeve, surrounds the winding I5. Said sleeve issplit at 24 and is connected to ground by a lead 25 which may be anextension of lead 2l. A protective covering of tape may also be woundaround the coil and sleeve structure to reinforce the sainestructurally. Shielding sleeve 23 is eiective to pick up theelectro-static capacity radiations emanating from conductor 3. andcarries the same to ground so that the current induced in winding l5 issubstantially free of any capacity components.

The coil unit and cable may be properly positioned and resilientlysupported in casing 5 by a yieldable insulating compound ,29. The latteris preferably injected into casing 5 under pressure through a smallopening while the casing is substantially evacuated so that the entirespace i within the same will be filled with the compound. The latter maybe injected in liquid form and permitted to. set te solid form eitherwith or without the application of heat. There. are a number of knowncompounds suitable for this purpose, such as for example, polymerizedCashew-nut shell oil. The openings 5 and l may be closed with suitablecovers (not shown) during the lling step and said covers may support agreased rod of suitable size in the place oi cable 8, sothat whenremoved a suitable passage will be providedl for ther cable.

Inl operation, whenever there is a change in the amount of currentflowing through conductor 8, therel will be a corresponding variation inthe magnetic fluxv lines surrounding the conductor and hence passingthrough coil M. If the variationY sufficiently rapid and of appreci ablemagnitude, a vflow of current will be induced in winding i5y when thesameis cutI by the magnetic flux lines. When conductor 8 forms a part ofa spark plug: lead, for example, the circuit including coil I4.v isshocked in toiexcitation whenever there is av ilow'bf energytlirough theconductor causingqihe, spark plug to nre. The signal thus. picked 'upfcoil M may: be. usefully employed apparatus' for investigating the oplveration of the Sentire, ignition vsystem of the engine.

The electrostatic. shield may, if desired, take ar difierent form fromthe sleeve. 23 around the coil.. Forv example, the, shield maybe in theform ofl a metal tube. 21l as illustrated by' dotted lines in Fig. 11.The enlarged `end orsaid tube` is soldered or otherwise suitably securedto the nipple 28 of opening.` 6 and extendsy through the centralopeningr of core l0 to: a position relatively close to the` nipple 29around opening l. The free end of tubel 2li will, of course, beadditionally supported and insulated from the, casing by the fillingcompound 29. The shield may also consist of two telescoping tubes, eachsecured to one of the. nipples 28J or 29 in the same manner thatI tube2,1 is secured.A At the telescoping ends,y the tubes may"l have asufficient diierence in diameters to permit the compound 26 to insulatethem from one another.

There is thus provided a novel and eflicient energy pick-up device whichmay be suitably designed for ready and quick installation in an electriclead for detecting variations in the flow of current through the lead.Novel means are also provided in the inductive pick-up unit comprehendedfor eliminating capacity components from the induced energy. The unit isof relatively simple and compact construction and yet sturdy andreliable.

Although only one embodiment of the invention has been illustrated anddescribed in the accompanying drawings and the foregoing specification,it is to be expressly understood that the invention is not. so limited.'It is not necessary, for example, to. provide a complete shieldingcasing in all installations. Various other changes: may be madeparticularly in the design and` ar` rangement of the parts illustratedwithouty departing from the. spirit and scope of the invention as itwill now be understood by those skilled, in the art. For a definition ofthe limits, of the invention, reference is had primarily to. theappended claims.

What is claimed is:

1. Apparatus of the class described comprising a metallic casing havingcable outlets in opposite sides thereof, an electrical conductorsupported in the casing and extending between said outlets, a laminatedcore of magnetic ilux conducting metal completely surrounding a sectionof said conductor in said casing, a coil closely surrounding only aportion of said core and insulated therefrom, a double-endedlongitudinally-split metallic sleeve substantiallysurrou-ndn ing theperiphery of said coil, means electrically connecting said core andsleeve to the casing, an electrical outlet in the wall of said casinghaving f at least one contact electrically connected to the highpotential end of said coil, and yieldable electrical insulationcompletely filling the remaining space in said casing and supportingsaid -f coil and core therein.

2. An induction coil unit as defined in claim 1 wherein said core.comprises` two cooperating U-shaped parts.

3. An induction coil` unit as defined in claim 1 wherein said core.comprises two cooperating U-shaped parts, said parts being securedtogether by means including a metallic strap.

Beiercps Cited in the le of this patent UNITED STATES PATENTS NumberNamey Date 783,533 Moody Feb. 28, 1905 1,629,132 Thordarson May 17, 19271,702,159 Grunow Feb. l2,` 1929 1,709,826 Austin Apr. 23, 19.291,830,541 Harris Nov. 3, 1931 2,081,979 Bentley June 1 1937 2,136,609Butterfield et al. Nov. 15,l 1938 2,170,048V punning et al. Aug. 22,19,39 2,183,355 Mauerer Dec. 12, 1939` 2,187,950 15111152.11 et, al,Jan. 23, 1940 2,214,915 Wehrlin Sept. 17, 1940 2,249,057 Stahl July 15,1941 2,327,774 Dickinson Aug. 24, 1943 2,408,211 Hodnette Sept. 24,`194.6 2,476,121 Smith, Jr. July 12,1949

FOREIGN PATENTS Number Country DateL 96,764 Austria Nov. 14, 1,938

